During the first project period, several methods were developed to replicate oral structures. These methods involved obtaining a negative replica in polyether, acetate tape, or silicone followed by fabrication of a positive duplicate of the original in epoxy or BIS-GMA resin. The positive can be used to study the structure of the original tooth or restoration over a wide range of magnification in the SEM. It was proposed that these methods be used to study acid etching patterns and remineralization of canine enamel by replications made in vivo. A comparison study is to be made on extracted teeth in vitro. A second study was proposed to examine the deterioration of amalgam margins via SEM analysis of replicas obtained in vivo in canine teeth. Amalgams will be prepared from conventional and copper rich amalgam alloy formulations. The in vivo study in dogs will also assist in overcoming any difficulties encountered in preparing to use the techniques intra-orally on human subjects in the dental clinic. BIBLIOGRAPHIC REFERENCES: N. Sarkar, G.W. Marshall, J.B. Moser and E.H. Greener: In Vivo and In Vitro Corrosion Products of Dental Amalgam. J. Dent. Res., 54, No. 5 (1975), 1031-1038. G.W. Marshall, N.K. Sarkar and E.H. Greener: Detection of Oxygen in the Corrosion Products of Dental Amalgam. J. Dent. Res., 54, No. 4 (1975), 904.